The invention relates to a four-stroke internal combustion engine control system of the type including an exhaust channel throttle flap for holding back exhaust gases during vehicle braking.
German Published Unexamined Application (DOS) No. 2,832,526 discloses a four-stroke internal combustion engine with an engine exhaust brake, in which a throttle flap holding back the exhaust gases during braking is arranged in the outlet channel, and in which the inlet and outlet valves are controlled by a cam shaft. A displaceable and/or rotatable shaft provided with stops is located in the region of the rockers. During braking, the stops can be shifted into the pivoting range of the rockers for the outlet valves to limit their stroke so that they just fail to touch the associated valve seats. At the same time, the limitation of the stroke of the outlet valves is selected so that during braking they are lifted off approximately 1/10 mm from the associated valve seats. This achieves the object of improving the engine exhaust brake in such a way that the outlet valves are prevented from impacting or are relieved of pressure during braking by simple means and without any reduction in the braking effect. The engine braking power therefore remains unaffected by this outlet-valve control.
In contrast to these engine exhaust brakes, German Patent Specification No. 1,057,385 discloses internal combustion engines with an engine brake, which achieve the braking effect in such a way that one of the gas-reversing valves is kept open permanently and that a substantial proportion of the compression work carried out by the internal combustion engine is nullified. However, the engine braking power which can be achieved in this way is only relatively slight.
An object of the invention is to increase the engine braking power in an internal combustion engine of the particular generic type.
According to the invention, this and other objects are achieved by providing an adjustable throttle valve in the engine exhaust channel and stroke limiting devices at each exhaust valve at the engine cylinders. A control arrangement is interconnected with the vehicle brake pedal for controlling the throttle valve and the stroke limiting devices in dependence on the travel path of the brake pedal.
In especially preferred embodiments the throttle valve is controlled by a compressed air circuit actuating device controlled by a piston attached for movement with the brake pedal and the stroke limiting devices are actuated by an engine oil pressure circuit controlled by electric switch members attached for movement with the brake pedal.
By means of the internal combustion engine according to the invention, such a high increase in the engine braking power can be achieved that, even where relatively large commercial vehicles are concerned, the system complies with existing statutory regulations and those to be expected in the future. The outlay in terms of construction is kept low because auxiliary forces, already available in any case in commercial vehicles, are used to control the actuating device and the limiting devices. The engine braking power can be varied according to requirements by means of the connection and disconnection of individual outlet valves or groups of outlet valves and as a result of combination with the engine exhaust brake.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment in accordance with the present invention.